Peritoneal dialysis system

ABSTRACT

Peritoneal dialysis system comprising pumping means, therapy data receiving means and processing means, said processing means being designed to process said therapy data and to impart a switching sequence to said pumping means characterized by the fact that said processing means are furthermore designed to impart a specific exchange profile for each exchange cycle.

FIELD OF INVENTION

The present invention relates to a peritoneal dialysis system which can conduct a specific peritoneal dialysis treatment.

The invention also relates to a method for determining a peritoneal dialysis treatment which is specific for each patient.

STATE OF THE ART

During a peritoneal dialysis session a liquid, the so called dialysate, is introduced many times into the peritoneal cavity in order to exchange toxins and liquid with the blood. The exchange takes place through the net of capillaries within the peritoneal membrane.

Examples of standard treatments are:

-   -   APD (Automatic Peritoneal Dialysis),     -   CAPD (Continuous Ambulatory Peritoneal dialysis),     -   CCPD (Continuous Cycling Peritoneal Dialysis),     -   TPD (Tidal Peritoneal Dialysis).

All state of the art treatments are characterized by exchanges with fixed volumes and dwells. However, those treatments are not taking into account the permanent change of patient characteristics after each exchange cycle.

It would therefore be more efficient to have another treatment which better follow the changes of patient characteristics during a treatment.

DESCRIPTION OF THE INVENTION

The above cited problems are solved with the peritoneal dialysis system according to the invention which comprises pumping means, therapy data receiving means and processing means, said processing means being designed to process said therapy data and to impart a switching sequence to said pumping means. The system according to the invention is characterized by the fact that said processing means are furthermore designed to impart a specific exchange profile for each exchange cycle.

In other words, the system according to the invention is designed to vary the exchange cycles during the treatment in order to better match the patient characteristics in a dynamic way.

In the following text, the treatment according to the invention is called DPD for Dynamic Peritoneal Dialysis.

The variation of the exchange cycles can be done in varying the injected volume of liquid and/or the dwell times and/or the extracted volume of liquid.

A more detailed description of the invention is presented below together with the following figures:

FIG. 1 illustrates the volume exchange with the peritoneal cavity.

FIG. 2 illustrates a state-of-the-art therapy

FIG. 3 illustrates a DPD treatment according to the invention.

Let us introduce the notation that will be used in relation with the DPD pattern. We remind that the injection-dwell-extraction pattern in peritoneal dialysis (PD) is made by several cycles i=1, . . . , N (see FIG. 1). The Vmax and Vmin in FIG. 1 represent respectively the maximum volume that can be introduced in the peritoneal cavity and the minimum volume reachable. In each cycle some fresh dialysate is injected (DVi), and extracted from the patient after a given dwell time (TDi). We refer to FIG. 2 for an explanation of the notation. The standard therapies nowadays in use APD, CAPD, CCPD, TPD etc. . . . , have a common property: the dwell times DTi and the injected volumes DVi are fixed with respect the number of cycle i=1; . . . ; N. It means that:

DT(1)=DT(2)= . . . =DT(N)

DV(1)=DV(2)= . . . =DV(N)

This is just the case represented in FIG. 2. It is obvious that by this way the standard PD treatments are somewhat rigid because there is no possibility to get DT(1)≠DT(2)≠ . . . ≠DT(N) and or DV(1)≠DV(2)≠ . . . ≠DV(N). Conversely, the DPD treatments provide this possibility and guarantee more flexibility. We refer to FIG. 3 as example of DPD. The reader should recognize easily the variability in dwell times and volumes that distinguish DPD with respect standard therapies by a comparison of FIGS. 2 and 3.

In order to build a DPD pattern we consider a set of input data concerning the therapy.

Preferably we consider as input the total therapy time (T_(tot)), the total dialysate volume available for the peritonal dialysis session (V_(tot)), the flow rate of the pumping means (q), the maximum dialysate volume that can be contained in the peritoneal cavity (V_(max)), the minimum dialysate volume reachable in the peritoneal cavity (V_(min)) and the number of cycles of the therapy (N).

The DPD method provides the injection-dwell-extraction pattern taking into account a set of constraints:

-   -   the therapy begin filling the peritoneal cavity up to Vmax,     -   the therapy must not be longer than the fixed total time Ttot,

${\sum\limits_{i = 1}^{N}{{TD}(i)}} = {T_{tot} - {2\frac{V_{tot}}{q}}}$

-   -   the total dialysate volume injected must be equal to the total         amount Vtot available,

${\sum\limits_{i = 1}^{N - 1}{{VD}(i)}} = {V_{tot} - \left( {V_{\max} - V_{\min}} \right)}$

-   -    the dwell times must be positive,

TD(i)>0, i=1, . . . N

-   -   the volume of dialysate into the peritoneal cavity must respect         the lower and the upper bounds Vmin and Vmax

0<DV(i)≦V _(max) −V _(min), i=1, . . . , N−1

-   -   the therapy end emptying the peritoneal cavity from Vmax to         Vmin,     -   Nmin is the minimum number of cycles needed to use the dialysate         available: Nmin=ceil(Vtot=(Vmax/Vmin)).

Based on the previous input data and constraints the DPD strategy provides the injection-dwell-extraction through the following iterative relations. The first set is used to choose the dwell times T D(i) of the DPD pattern as follows:

$\left\{ {\quad\begin{matrix} {{{{TD}\left( {i + 1} \right)} = {\left( {\alpha + {\gamma \; i}} \right){{TD}(i)}}},{i = 1},\ldots \mspace{14mu},{N - 1}} \\ {{{TD}(1)} = \frac{T_{tot} - {2\frac{V_{tot}}{q}}}{1 + {\sum\limits_{j = 1}^{N - 2}{\prod\limits_{i = 1}^{j}\; \alpha}} + {\gamma \; i}}} \end{matrix}} \right.$

where,

-   -   α is the parameter which fix a base for the ratio T D(i+1)/T         D(i), β is the parameter which allows to change the ratio T         D(i+1)/T D(i) with respect the number of the cycle,     -   TD(1) is computed to respect the total therapy time Ttot

The second set is used to choose the volumes injected DV(i) of the DPD pattern as follows

$\left\{ {\quad\begin{matrix} {{{{DV}\left( {i + 1} \right)} = {\left( {\beta + {\delta \; i}} \right){{DV}(i)}}},{i = 1},\ldots \mspace{14mu},{N - 2}} \\ {{{DV}(1)} = \frac{V_{tot}}{1 + {\sum\limits_{j = 1}^{N - 2}{\prod\limits_{i = 1}^{j}\; \beta}} + {\delta \; i}}} \end{matrix}} \right.$

where,

-   -   β is the parameter which fix a base for the ratio DV(i+1)=DV         (i),     -   δ is the parameter which allows to change the ratio         DV(i+1)=DV (i) with respect the number of the cycle     -   V D(1) is computed to respect the total dialysate volume Vtot         available. If γ=0, α=1 we obtain TD(i+1)=TD(i) and If δ=1, β=1         we obtain DV (i+1)=DV (i). This parameters set up allows to         obtain standard treatments by the DPD methodology.

In order to guarantee the execution of the DPD pattern to pumping means the outputs produced are:

-   -   the dwell sequence T D(i); i=1; . . . ; N,     -   the volume sequence DV(i); i=1; . . . ; N−1,     -   the switching sequence for the pumping means execution,

t0=0;

tk+1=tk+DT(k); k=0; . . . ; 3N+1

where DT (k) represent the time needed in each cycle for the injection phase, the dwell and the extraction phase.

Of course the invention is not limited to the above examples. For instance other equations can be used for defining the varying parameters TD and DV. 

1. Peritoneal dialysis system comprising pumping means, therapy data receiving means and processing means, said processing means being designed to process said therapy data and to impart a switching sequence to said pumping means characterized by the fact that said processing means are furthermore designed to impart a specific exchange profile for each exchange cycle.
 2. Peritoneal dialysis system according to claim 1 wherein said processing means are designed to vary the volume of liquid injected in each exchange cycle.
 3. Peritoneal dialysis system according to claim 1 wherein said processing means are designed to vary the volume of liquid extracted in each exchange cycle.
 4. Peritoneal dialysis system according to claim 1 wherein said processing means are designed to vary the dwell time in each exchange cycle.
 5. Peritoneal dialysis system according to claim 1 wherein said therapy data include the total therapy time (T_(tot)), the total dialysate volume available for the peritonal dialysis session (V_(tot)), the flow rate of the pumping means (q), the maximum dialysate volume that can be contained in the peritoneal cavity (V_(max)), the minimum dialysate volume reachable in the peritoneal cavity (V_(min)) and the number of cycles of the therapy (N).
 6. Peritoneal dialysis system according to claim 1 wherein said processing means are capable to determine each dwell time TD(i) according to the following system of equations: $\left\{ {\quad\begin{matrix} {{{{TD}\left( {i + 1} \right)} = {\left( {\alpha + {\gamma \; i}} \right){{TD}(i)}}},{i = 1},\ldots \mspace{14mu},{N - 1}} \\ {{{TD}(1)} = \frac{T_{tot} - {2\frac{V_{tot}}{q}}}{1 + {\sum\limits_{j = 1}^{N - 2}{\prod\limits_{i = 1}^{j}\; \alpha}} + {\gamma \; i}}} \end{matrix}} \right.$ where, α is the parameter which fixes a base for the ratio T D(i+1)/T D(i), D is the parameter which allows to change the ratio T D(i+1)/T D(i) with respect the number of the cycle, TD₍₁₎ is computed to respect the total therapy time T_(tot).
 7. Peritoneal dialysis system according to claim 1 wherein said processing means are capable to determine each volume injected DV(i) according to the following system of equations: $\left\{ {\quad\begin{matrix} {{{{DV}\left( {i + 1} \right)} = {\left( {\beta + {\delta \; i}} \right){{DV}(i)}}},{i = 1},\ldots \mspace{14mu},{N - 2}} \\ {{{DV}(1)} = \frac{V_{tot}}{1 + {\sum\limits_{j = 1}^{N - 2}{\prod\limits_{i = 1}^{j}\; \beta}} + {\delta \; i}}} \end{matrix}} \right.$ where, β is the parameter which fix a base for the ratio DV(i+1)=DV (i), δ is the parameter which allows to change the ratio DV(i+1)=DV (i) with respect the number of the cycle. V D(1) is computed to respect the total dialysate volume Vtot available.
 8. Peritoneal dialysis system according to claim 1 claims wherein said processing means are designed to determine the switching sequence as follows: t0=0, t _(k+1) =t _(k) +DT(k); K=0; . . . ; 3N+1 where DT(k) represents the time needed in each exchange cycle for the injection phase, the dwell and the extraction phase.
 9. Method for determining a peritoneal dialysis treatment characterized by the fact that the liquid exchange profile is varying from one exchange cycle to the other.
 10. Method according to claim 9 wherein the dwell time TD varies from one exchange cycle to the other.
 11. Method according to claim 9 wherein the volume of liquid injected DV varies from one exchange cycle to the other.
 12. Method according to claim 9, wherein the volume of liquid extracted DV varies from one exchange cycle to the other.
 13. Method according to claim 9 wherein each dwell time TD(i) is determined according to the following system of equations: $\left\{ {\quad\begin{matrix} {{{{TD}\left( {i + 1} \right)} = {\left( {\alpha + {\gamma \; i}} \right){{TD}(i)}}},{i = 1},\ldots \mspace{14mu},{N - 1}} \\ {{{TD}(1)} = \frac{T_{tot} - {2\frac{V_{tot}}{q}}}{1 + {\sum\limits_{j = 1}^{N - 2}{\prod\limits_{i = 1}^{j}\; \alpha}} + {\gamma \; i}}} \end{matrix}} \right.$ where, α is the parameter which fixes a base for the ratio T D(i+1)/T D(i), β is the parameter which allows to change the ratio T D(i+1)/T D(i) with respect the number of the cycle, TD₍₁₎ is computed to respect the total therapy time T_(tot).
 14. Method according to claim 8 wherein each volume injected DV(i) is determined according to the following system of equations: $\left\{ {\quad\begin{matrix} {{{{DV}\left( {i + 1} \right)} = {\left( {\beta + {\delta \; i}} \right){{DV}(i)}}},{i = 1},\ldots \mspace{14mu},{N - 2}} \\ {{{DV}(1)} = \frac{V_{tot}}{1 + {\sum\limits_{j = 1}^{N - 2}{\prod\limits_{i = 1}^{j}\; \beta}} + {\delta \; i}}} \end{matrix}} \right.$ where, β is the parameter which fix a base for the ratio DV(i+1)=DV (i), δ is the parameter which allows to change the ratio DV(i+1)=DV (i) with respect the number of the cycle. V D(1) is computed to respect the total dialysate volume Vtot available. 